Oxidation of the anti-Parkinsonian agent carbidopa by tyrosinase was investigated. The products of this reaction were identified as 3-(3, 4-dihydroxyphenyl)-2-methylpropanoic acid and 6, 7-dihydroxy-3-methylcinnoline. These results demonstrate that after oxidation of the catechol moiety to an o-quinone either a redox exchange with the hydrazine group or a cyclization reaction occur. The cyclization product underwent additional oxidation ...
